天線系統之等效電路生成

Abstract

本文提供新的觀點來探討現有一組經由向量網路分析儀得到天線的量測數據,則可將此天線轉換成含有電阻、電感、電容或壓控電流源(voltage controlled current source, VCSS) 等元件的等效電路。文中比較了兩種生成等效電路的方法,第一種是經由複數跳頻 (complex frequency hopping, CFH) 和狀態空間(state space) 等方法來生成等效電路,而第二種方法是由向量擬合法(vector fitting, VF) 和極點留數形式(pole-residue form) 得到對應的等效電路,於是分別由上述的兩種方法將單端輸入單端輸出(single input single output) 系統的量測數據轉換成等效電路。而為了驗證兩種方法都能有效的生成等效電路,於是就做了兩個實驗,第一個實驗是將單極天線量測的數據分別經由兩種方法來生成等效電路,而另外一個實驗是將此單極天線置於依有透氣狹縫的金屬箱內,來模擬天線在腔內輻射,同樣的也經由兩種方法來生成等效電路。然後經由電路模擬軟體SPICE來驗證生成的等效電路是否可以準確的近似頻率響應,而最後會對生成的等效電路做比較。

The thesis compares two algorithms for generating broadband equivalent circuits for highly resonant antenna systems. The first algorithm applies the complex frequency hopping (CFH) to generate equivalent circuits with resistors, capacitors and voltage controlled current sources (VCCSs). The second one applies vector fitting (VF) to generate equivalent circuits consist of resistors, reactors, capacitors and inductors. In order to test the above algorithms for generating equivalent circuits based on real-world measurement data, we build a monopole antenna attached to a finite ground plane and we build a copper box with a narrow ventilation slot. We measured the input impedances of both the standalone monopole antenna and the antenna enclosed in the copper chasis. The results demonstrate that both algorithms are very stable for generating broadband equivalent circuits for the resonant antenna system. Furthermore, we also identify the relationship between poles of the antenna transfer functions and the resonant frequencies.